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Date: Mon, 10 Sep 2012 15:21:20 +0300
From: Gleb Natapov <gleb@redhat.com>
Message-ID: <20120910122120.GA20907@redhat.com>
References: <5034F587.4000403@dlhnet.de> <5048BA0F.3070300@redhat.com>
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Subject: Re: [Qemu-devel] memtest 4.20+ does not work with -cpu host
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Lieven <pl@dlhnet.de>, Avi Kivity <avi@redhat.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On Mon, Sep 10, 2012 at 02:15:49PM +0200, Paolo Bonzini wrote:
> Il 10/09/2012 13:52, Peter Lieven ha scritto:
> >> dd if=/dev/cpu/0/msr skip=$((0x194)) bs=8 count=1 | xxd
> >> dd if=/dev/cpu/0/msr skip=$((0xCE)) bs=8 count=1 | xxd
> > it only works without the skip. but the msr device returns all zeroes.
> 
> Hmm, the strange API of the MSR device doesn't work well with dd (dd
> skips to 0x194 * 8 because bs is 8.  You can try this program:
> 
There is rdmsr/wrmsr in msr-tools.

> #include <fcntl.h>
> #include <stdio.h>
> #include <stdlib.h>
> 
> int rdmsr(int fd, long reg)
> {
>     char msg[40];
>     long long val;
>     sprintf(msg, "rdmsr(%#x)", reg);
>     if (pread(fd, &val, 8, reg) < 0) {
>         perror(msg);
>     } else {
>         printf("%s: %#016llx\n", msg, val);
>         fflush(stdout);
>     }
> }
> 
> 
> int main()
> {
>     int fd = open("/dev/cpu/0/msr", O_RDONLY);
>     if (fd < 0) { perror("open"); exit(1); }
>     rdmsr(fd, 0x194);
>     rdmsr(fd, 0xCE);
> }
> 
> Paolo
> --
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--
			Gleb.